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    <title>Document</title>
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<script>
    //原型对象的应用 扩展内置对象方法
    // console.log(Array.prototype);

    //自定义数组原型对象方法

    //注意：数组和字符串内置对象不能给原型对象覆盖操作Array.prototype={},只能是Array.prototype.xxx=function(){}的方法。
    Array.prototype.sum = function () {
        var sum = 0;
        for (var i = 0; i < this.length; i++) {
            sum += this[i]
        }
        return sum
    }

    Array.prototype.multiplication = function (num1, num2) {
        return num1 * num2
    }
    const arr = [1, 2, 3, 4]
    console.log(arr.sum());
    console.log(arr.multiplication(10, 50));
    console.dir(Array);
    const arr2 = new Array(11, 22, 33)
    console.log(arr2.sum());
</script>

</html>